Injurious blunt trauma to a human brain should be understood as delivery of mechanical waves to the human brain which then undergoes intercellular and intracellular changes such as findings associated with diffuse axonal injury and cerebral vasospasm without bleeding from cerebral blood vessels. Changes in electrochemical, molecular and signaling pathways of tissue must occur, including integrin mediated activation of Rho kinase and phenotypic switches indicative of vascular remodeling. As of now, we are at an early stage of our understanding of pathogenesis of the blunt trauma and its consequences.
In the previous patent application (U.S. patent application Ser. No. 15/083,407) for a protective headgear for the human brain, I proposed that boundary effect of mechanical waves of the blunt trauma would be exploited for reducing an amplitude of the mechanical waves delivered to a brain tissue, using a multi-layered protective shell to increase number of boundaries inside the protective shell as practically many as possible to a point there would not be a serious tissue injury to the brain tissue. Of materials transferring energy from the mechanical waves, air (gas) has by far a lowest density of molecules per area, thereby having a lowest index of transfer function as a medium for the mechanical waves. I proposed that the protective shell be configured to be pressurized with a gas and to let the gas released upon an impact from the blunt trauma. If an amplitude of the mechanical waves of a blunt trauma does not exceed a resistive pressure of an impacted gas inside the protective shell, the amplitude of the mechanical waves will go through the layered boundaries in the way described above except that the impacted gas would not be released and some of the mechanical waves will transform to heat and some others transmitted to the brain tissue. If the amplitude of the mechanical waves of the blunt trauma exceeds the resistive pressure of the impacted gas inside the protective shell, then a portion of the impacted gas will be released from the protective shell upon the impact of the blunt trauma. It results in a depletion of a portion of an impact energy carried in the impacted gas, which is a decrease in the amplitude of the mechanical waves reaching the brain tissue. While the number of the layered boundaries of the protective shell is fixed once manufactured, the pressure of the gas in the protective shell can be variably adjustable based on a weight of a person wearing the protective shell and anticipated types and scenarios of an injury. Combining both methods for the protective shell would therefore be more advantageous to using either method alone.
Incident mechanical waves traveling in an ambient air do not undergo phase change upon hitting a medium having a higher impedance to mechanical waves than that of air. Some of the mechanical waves will be reflected off the medium without the phase change, and some will be transmitted through the medium. If the medium has a finite dimension through which the transmitted mechanical waves travel, the transmitted mechanical waves come out from the other side of the medium to the ambient air. The transmitted mechanical waves coming out from the medium to the ambient air then undergo phase reversal, similar to the phase reversal of the mechanical waves reflecting off a lower impedance medium. A part of energy (amplitude) of the mechanical waves is known to be lost during transition from a medium having a higher impedance to a medium having a lower impedance to mechanical waves. If a first layer of a medium of a higher impedance to mechanical waves is adhered in tandem to a second layer of a medium of a lower impedance to mechanical waves forming a two-layered boundary, incident mechanical waves to the first layer will be reflected off an outer surface of the first layer in phase and some of the incident mechanical waves will be transmitted to the second layer out of phase while dissipating energy (reducing amplitude) at a border between the first and second layers. The transmitted mechanical waves through the second layer will come out through an inner surface of the second layer out of phase a second time, which results in mechanical waves in phase with the original incident mechanical waves. It also results in dissipation of the energy of the mechanical waves a second time at a border between the outer surface of the second layer and the ambient air. A part of the transmitted mechanical waves through the second layer will bounce back in phase at the outer surface of the second layer bordering the ambient air, which travels continuously through the first layer without phase change. Upon exit through the outer surface of the first layer, the mechanical waves emerge out of phase. It results in dissipation of the energy of the mechanical waves a third time at a border between the outer surface of the first layer and the ambient air. The aforementioned process of reflections and transmissions of mechanical waves across the two-layered boundary contributes to a loss of the energy (reduction in amplitude) of the mechanical waves from an original state of the energy.
In a closed system which stacks up in parallel multiple two-layered boundaries, the loss of the energy of the mechanical waves through the reflections and transmissions across the two-layered boundary could be maximized if each two-layered boundary is separated from the other two-layered boundary without physical contact between them. The mechanical waves travel through physical contact points between two opposing sets of the two-layered boundary if they maintain a contact with each other when the mechanical waves are delivered. Furthermore, if a first two-layered boundary has an impedance to the mechanical waves different from that of a second two-layered boundary, there will be an additional loss of the energy of the mechanical waves at a time the mechanical waves travel from the first two-layered boundary to the second two-layered boundary if transmission of the mechanical waves from the first to the second two-layered boundaries is synchronized with reversible physical contact between the first and the second two-layered boundaries.
In a pressure zone immediately adjacent to the outer surface of the two-layered boundary facing the incident mechanical waves from a blunt trauma, reflected mechanical waves off the outer surface add to the incident mechanical waves toward the outer surface. As the reflected mechanical waves are in phase with the incident mechanical waves, addition of the reflected mechanical waves to the incident mechanical waves double up an amplitude of the mechanical waves. The doubling-up of the amplitude of the mechanical waves occurs at a region of the outer surface of the two-layered boundary where the incident mechanical waves come in contact with and in the pressure zone immediately adjacent to the outer surface, thereby increasing an energy of an impact of the blunt trauma to the region of the outer surface. Process of the doubling-up of the amplitude of the mechanical waves could be disrupted if a gas in the pressure zone as a medium receiving the doubled-up amplitude of the mechanical waves is taken away from the pressure zone as soon as the doubled-up amplitude of the mechanical waves is delivered to the gas. It can be accomplished by venting the gas from a distended compressible gas cell affixed to the outer surface at a time and a place the reflected mechanical waves add to the incident mechanical waves.